Insulin-dependent diabetes mellitus (IDDM) is an autoimmune disease characterized by selective destruction of the insulin secreting ?-cells found in pancreatic islets of Langerhans. While ?-cell destruction is mediated by T-lymphocytes-dependent mechanisms, the pathways that initiate this autoimmune attack are unknown. The low concordance rate for diabetes development among identical twins (less than 40%) indicates that environmental factors, in addition to genetic predisposition, participate in the induction of autoimmune diabetes. Viral infection is one environmental factor that has been proposed to initiate ?-cell damage during the development of diabetes. The broad goals of this research are to elucidate the biochemical mechanisms by which virus infection contributes to the loss of ?-cell function and viability during diabetes development. Using a virus known to induce diabetes in susceptible mice (Encephalomyocarditis virus, EMCV), we have identified a novel antiviral response that is characterized by the expression of inflammatory genes (inducible nitric oxide synthase, iNOS and interleukin (IL)-1) that are known to damage ?-cells. This inflammatory response is regulated by the CC chemokine receptor Ccr5, and functions to attenuate virus replication. The inflammatory response does not require TLR3 or mda5, two double-stranded RNA sensors known to regulate the production of type 1 IFN. This application will test the hypothesis that the early inflammatory response contributes to virusinduced diabetes through Ccr5 signaling in macrophages or aberrant regulation of Ccr5 expression by ?-cells. There are three specific aims: 1) To test the hypothesis that Ccr5 controls the macrophage response to EMCV infection through G-protein coupled receptor-activated signaling cascades that regulate both transcription and translation of inflammatory genes. 2) To test the hypothesis that CCR5-deficiency will attenuate diabetes development in response to EMCV infection in genetically susceptible mice. 3) To test the hypothesis that aberrant expression of CCR5 in ?-cells increases the susceptibility of these cells to damage and the induction of diabetes in response to virus infection. A number of biochemical, molecular, immunological, histochemical, and transgenic techniques will be utilized to investigate the cellular pathways through which viral infection stimulates macrophage activation and modulates ?-cell function and viability. It is hoped that insights into regulation of macrophage and ?-cell responses to virus infection gained from these proposedstudies will influence the design of therapeutic strategies aimed at the prevention of this debilitating disease.